woody

The 4 speed was an Ossa Pennine, their first trials bike developed by Mick in 1967/8 and which evolved into the 5 speed MAR in 1971. The 4 speed was available in the US as on the promotional video people are riding them at one of Mick's schools They were dark green with yellow stripes on tank and mudguards, production version looked more like an enduro/scrambles bike than a trials bike I think the official Ossa name was Pluma

Yes the horn goes there although I've never seen one. Probably some of the specialists ion Spain may sell them as they do a lot of original and repro parts. In the UK, no idea apart from being luck on ebay - but the chances of one working if you found one.... This place has a big range of parts http://www.motosdelabuelo.com/

Worth loads of money they are. All the Bultaco engines are essentially the same carcass, just different states of tune and gears to suit their application. The outward appearance changed in early seventies when they went from the round barrel and rounded cases to the square barrel and slimmer cases as fitted on your 175

125 frame probably isn't any smaller or much lighter as the 125 motor still uses full size crankcases. Apart from the twin downtubes, the rest of it looks like a 250 frame from '76 to '78 which used the shorter forks. It even has the bend at the top of the downtubes. I think the only reason the 125 appears to be a smaller bike is the wheels are 20/17 so it sits a bit lower, there is only about an inch or so difference in height between 125 and bigger bikes. The 125 frame was supposedly a prototype for the 250/325 bikes but discarded in favour of continuing with the single downtube (not sure how that would have worked with the side exhaust port unless they were developing a new cylinder) Overall it was prbably a bit lighter but much of that may have come from the smaller top end and possibly a smaller crank assembly A friend of mine had a new 125 and it was truly gutless

The 175 uses the same frame as the 250cc (actually 238cc) model 190 Sherpa. The 250 frame from '76 to '78 had the bend at the top of the downtube. The motor is a 250 with cylinder sleeved down to 174cc. This capacity was basically done for rental companies in holiday resorts as the maximum capacity that could be ridden without a licence was 175. I think most of the 175 bikes were for the rental market with dual seats (which may explain the longer rear frame loop than a M190) but some were made as 175 Sherpa T. Don't know about them having a different crank assembly or lighter flywheel but converting to 250 is a top end swap or boring back to 250 (not sure if the head would need modifying for the bigger bore, I've never had one apart so don't know if the 175 has a different combustion chamber) If you need more info speak to Dave Renham at In Motion The 175 uses a 25mm carb whereas the 250 had a 27mm. The 250 would run fine on a 25mm as the early 325 engines used a 25mm carb. The 175 had a higher 1st gear than the other bikes but the rest were the same as the 250/325.

The 349/4 is a very underrated bike, handles well, great power, grips well, just let down by the clutch if ever it needs to be used in sections, I had the 350 version. The 330 was a seperate model though, completely different from the 349 and a different chassis prefix from 51

Not sure you can date a 349 from the frame number as I don't think it is recorded anywhere. There were three models types of 349 and all start 51. You need a picture really

HFS internals won't change the damping as they are for spring rate only. If you're going to use them you might just want to get the clubman version which is springs only. The expert version has an air cartridge to further enhance spring rate but I tried one and the cartridge was a real pain to set up with the correct pressure. A friend has the clubman version and they work fine which is what I'd get if I was going HFS again (I sold the expert version it frustrated me that much). There are also Magical springs which work well You might want to look at the piston on the end of the damper rod. From a certain year these were fitted with fibre seals to help sealing and these have usually worn down letting oil past the piston which reduces damping effect. You can't buy new replacements but you can make the out of the correct thickness PTFE card. Early models didn't have the seal and are just a plain steel bush so if properly worn and damping is really poor with constant topping out there isn't much you can do other than make new ones. 15W oil is heavy but if that's what it needs to help your damping, then that's what you have to use but mine varies between 5 and 10w

Might be worth also checking the swingarm to see if it's bent. I had one which must have been clattered on one side as both arms were pointing to the right when you looked at it from the back of the bike with the wheel out and I had to straighten both back into line using another arm as a guide. If you look at your bike from the back are the shocks upright as if the are leaning a bit, it could show the swingarm is out of line? You shouldn't have to offset snail cams really, I have a few Bultacos and have never had to do that. The chainguards all run close and rub a bit, even the tensioner can rub on them. The spindle on the speedo side is wasted for the threads so a larger diameter washer is needed where the solid part of the spindle protrudes by a mill or two and has to be that thick otherwise the spindle nut won't pull up against the arm, just the ridge on the spindle. You let Spence loose on your wheels..... only joking, he's a good bloke. I've probably ridden past your 'back garden' on many occassions over the years

The parts you mention should be easy to find, carb was 25mm Amal originally but not really worth risking an old used one. Can be replaced with a 26mm Amal/Mikuni/OKO - Mid Atlantic trials have decent deals on OKO carbs. Gear change lever can be had new although used come up on ebay. You need one from a bike with the same side casing as yours which was fitted to all Sherpas from your model onwards, as earlier models have a wider bend for the different shaped clutch casing. Kickstarts again, new or used. Tank/seat unit may prove difficult, not sure if anyone in the States reproduces them, used come up on ebay but may need repair and sealing against ethanol fuel. Airboxes come up fairly often on ebay and the same one was used on the 71 onwards Sherpa to your model, also similar year Alpinas. The outlet to the carb needs to exit from the bottom left of the airbox, so that it clears the sidepanel of the tank/seat unit, not from top right. One from a same year Alpina should also fit. Brake pedal new or used, if used it needs to be from a model from '68 up to your model. Later pedals will fit if you're not bothered about original look. The rear hub was unique to your model and the one before it (124/125) and would be hard to find. A later hub from the next model onwards will fit with no mods other than a different length spacer might be needed (if you meant a brake plate rather than brake hub, a Pursang brake plate may fit as your model Sherpa hub was based on a Pursang one) As the previous poster said, Hugh's Bultaco should give you all the info you need. If you have to split the engine be aware that although gearbox and clutch internals may look the same, there are subtle differences between some models and later parts may not interchange with your crank cases in the case of gearbox, or mainshaft in the case of clutch hub and basket

You had the order correct initially, there is no spacer between brake plate and swingarm The clearance is tight anyway, but the guard should fit although very close to the tyre so you will probably get some rub occasionally. Has the wheel been rebuilt with the wrong offset at some time maybe? What tyre is it? Looks like a Pirelli which is blown up quite hard? It may rub less with normal trials pressure

The bushes and seals on Falcons are standard sizes so you can get them from most bearing stockists. You can use air to re-gas them using a mountain bike shock pump, it doesn't have to be nitrogen.

There is also a very small seal that fits inside the final drive sleeve gear shaft, you need to replace that as well as the big one around the outside of the sleeve gear shaft. Also check the bush that sits between the seal and the gear shaft as these can get worn by debris underneath the seal which means there may no longer be a good contact between it and the ID of the seal. I don't think they're available new but remember if you have to get one made they need the recess on the inner side fo r the O ring Re; the broken bolt on the shock mount, drill a piece of bar in one end to fit over the protruding part and weld them together. The heat often helps free of the threads if they've corroded in and the leverage on the bar helps turn it. If it snaps off you're no worse off really as drilling out is the final option For info, you don't need a speedo fitted for an MOT, only required when actually using the bike on the road, so for the MOT you could just remove it

Nice bike, I've got on myself to restore one day. Any reason you've routed the aircleaner hose to carb inside of the sidepanel instead of though the slot? (other than they're a bugger to fit...) Forgot to mention the J on the headstock. This type of stamping has been mentioned before in other topics but no-one seems certain of what they represent. None of my bikes have them so not present on all

Footrests are Miller conversions as the originals are flat plate that don't fold. The rear brake pedal is probably a Miller mod as well, moving it to the inside which is where model 49 onwards pedals were located.The 27 had it behind the footrest as you say.

If the key isn't a good fit in the slot, it can easily ride up the back of the slot when fitting the flywheel and this isn't always apparent when assembling, meaning that the flywheel isn't fully home on the shaft when tightened. As you say, best bet is to get a new key, loctite it in, let it set and then fit the flywheel. Most of the engines I've had have had some wear of the slot, so this is what I always do. These flywheels coming loose isn't uncommon if it isn't fitted perfectly The single sided weight is standard on the later 250, from M158 onwards I think. Earlier 250 had a double sided weight, as do the 350 models

Just wondering why you think that.? The frame is probably an M91/92 series 2 but could be a 124/125 or 150/151 (250 and 325 from that era are the same visually so can't be told apart) Definitely not 158. The forks are M92 as is the chrome exhaust (which will bolt straight onto a 250 engine from '75 onwards)

They're both fibreglass, Ossa only fitted fibreglass at the factory. Only UK bikes had alloy tanks. The MAR alloy tank is a different shape from the glass tank, the Gripper alloy tank is the same shape but the tank and side panel are seperate units on UK bikes and the tank didn't use the front fixing bolts

You're never going to get an answer you can trust in 100%. If I was buying one I'd line it. A few years back I bought a tank for my 340 Sherpa and never got the chance to see if it was resistant or not as it split first time out along the seam where the upper and lower mouldings are joined (I think it was there anyway) The quality was poor and if held up to the light, looking through the filler cap hole you could see through the bottom in places, it was that thin. The quality of some repro parts isn't always good

They aren't engine mounts that have been removed, the lower front engine mount, where fitted (not on 5 speed trials engines) is central so where something has been removed is the wrong place for a front lower engine mount. It's possibly had case savers welded on at some point which may have been removed. Can't help with the upper mounts as I can't really see them from the pictures but the M80 doesn't have brackets there.It's nearly 50 years old so unless you know the history, previous owners could have fitted all manner of things. No idea what the G is, never seen that before, could signify the country it was exported to if not a UK bike originally?

It's not a split washer, the two halves locate in the groove in the spline and sit behind the big weight which sits up against them when tightened up. They also double up for use with the tool to remove the taper as PMK's photos show They weren't used as a part in the MAR engine so I guess they must have been available along with the puller from Ossa agents. Before you try and remove it measure the length as there are three different lengths for these. You'll need to know which one if trying to source a replacement should it break

There is a Pursang one that will do the job https://www.inmotiontrials.com/product/pursang-mk11-chain-rubber-slipper/

It's very difficult. This is only a suggestion as sometimes they come out, sometimes not. Remove the bushes from either side to allow more movement. Remove the timing cover, detach the spring from the tensioner arm and remove the pad, then you might just wriggle it out. What I did was take some off the end of the shaft on the timing side, either cut t or ground it can't remember, while still in the bike which made it a lot easier to get out. Because I'd lost enough length to drill another split pin hole I drilled and tapped the end of the shaft to 6mm so that when it went back in I fitted a bolt and penny washer instead of a split pin to stop it sliding through the bush. The same can be done to the other side once it's out but probably not necessary

Your clutch case should look like this, you can see the plug underneath https://www.ebay.co.uk/itm/Bultaco-Lobito-Pursang-Alpina-175-clutch-engine-case-cover-cap/172934687132?epid=7007483100&hash=item2843b5e99c:g:19UAAOSwnw9Z5~gd In your photo the original gearbox drain plug is the one behind the one you are pointing to, although I can't see that it has a drain bolt in it. The one you are pointing to is something that someone has added, maybe made their own gearbox drain if the original is damaged. I can't tell where exactly it's positioned but could also be a drain for the ignition should water get in there The casting on the other side is for a speedo drive which is a hangover from older engines. Thyey weren't used on later bikes, It's blank and isn't drilled

There is only one place I know of that does them and they are a repro not NOS judging by the kinks in the bend - Frankie Mountain If yours is good enough have it re-chromed as at least you know it fits properly. Some pattern parts.... http://www.frankiemountain.com/en/compra/ossa-mick-andrews-exhaust-pipe-chrome-new-ossa-mar-exhaust-250cc-1421